Structural brain abnormalities associated with cognitive impairments in bipolar disorder

Area of Science:

• Neuroscience
• Psychiatry
• Neuroimaging

Background:

• Cognitive impairment is a key feature of bipolar disorder (BD), persisting even during remission.
• The precise brain mechanisms underlying cognitive deficits in BD are not fully understood, hindering effective treatments.
• Investigating brain morphology in remitted BD patients can elucidate these mechanisms.

Purpose of the Study:

• To examine the relationship between brain structural abnormalities in the dorsal prefrontal cortex (PFC) and hippocampus and cognitive deficits in remitted BD patients.
• To identify specific morphological correlates of cognitive impairment in bipolar disorder.

Main Methods:

• Structural MRI and neuropsychological assessments were conducted on 153 remitted BD patients and 52 healthy controls.
• Patients were categorized into cognitively impaired (n=91) and cognitively normal (n=62) groups based on performance.
• Comparisons of dorsal PFC thickness/volume, hippocampus shape/volume, and total white/grey matter volumes were made between groups.

Main Results:

• Cognitively impaired BD patients showed increased left dorsomedial PFC thickness compared to normal patients and controls.
• No significant differences in hippocampal volume or shape were observed between patient subgroups and controls.
• Cognitively impaired patients had reduced total cerebral white matter volume, which correlated with poorer neuropsychological performance.

Conclusions:

• Cognitive impairment in bipolar disorder is associated with cerebral white matter deficits.
• Morphological changes in the dorsomedial PFC may be linked to white matter abnormalities in BD.
• These findings suggest that white matter integrity plays a crucial role in cognitive function in remitted bipolar disorder.